Surely bathrooms are something we can produce faster than the rate at which population increases.

people can destroy things faster than you can build or even maintain them is the problem.

it's mean to identify the certain people or hold them accountable, though, so we don't.

Your argument is unrelated to the global population.

It probably isn't as much about population growth as the increasing wealth gap. My hypothesis would be that a society where people don't feel fair distribution of wealth is more prone to this 'abuse' that you call 'overuse'.

I think it's mostly drug addicts.

Drug addicts don't become addicts all of the sudden. Lots of people with no place to go resort to awful things, people that feel like they have no place in society do not see a reason to take care of it. It doesn't make it right, but that doesn't mean we shouldn't try to address the root cause.